力扣每日一题2021-10-03分数到小数

• 166.分数到小数
• • 题目描述
  • 思路：高精度除法

分数到小数

每一位小数是通过*10再除余计算的。而循环小数可以通过判断被除数有没有出现过，出现的位置在哪来判断（哈希记录）。

class Solution:
    def fractionToDecimal(self, numerator: int, denominator: int) -> str:
        def hdiv(dividend, divisor, precision=0):
            if (dividend > 0 and divisor > 0) or (dividend < 0 and divisor < 0):
                flag = 1
            else:
                flag = -1
            dividend = abs(dividend)
            divisor = abs(divisor)
            quotient = dividend // divisor
            remainder = dividend % divisor
            if remainder == 0:
                return str(quotient * flag)
            ans = [str(quotient), '.']
            repeats = dict()
            i = 0
            while i < precision:
                dividend = remainder * 10
                quotient = dividend // divisor
                remainder = dividend % divisor
                if dividend in repeats:
                    ans.insert(repeats[dividend], '(')
                    ans.append(')')
                    break
                ans.append(str(quotient))
                repeats[dividend] = i + 2
                if remainder == 0:
                    break
                i += 1
            if precision == 0:
                ans.pop(1)
            if flag == -1:
                return '-' + ''.join(ans)
            return ''.join(ans)
        return hdiv(numerator, denominator, 10000)